This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to filed on the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a battery accumulating apparatus for use in a low altitude satellite use power supply apparatus, an electric motorcar use power supply apparatus, or the like.
In this connection, herein, for the convenience of explanation, a low altitude satellite use power supply apparatus will be described.
2. Description of the Related Art
FIG. 6 is a structural view of the low altitude satellite use power supply apparatus using a conventional storage battery such as a Nixe2x80x94Cd (Nickel Cadmium) battery. In FIG. 6, numeral 1 is a solar battery, numeral 2 is a shunt apparatus to consume surplus power generated in the solar battery, and numeral 3 is a power controller into which a current from the solar battery 1 is input through the shunt apparatus 2, and which supplies a current to a charging controller 4a and a load 6, and when the generated power of the solar battery 1 is lowered, which controls the charge controller 4a so that the current is supplied to the load 6 by discharging the storage battery 5. The charge controller 4a is a charge controller which receives an output from the power controller 3 and supplies a current to the storage battery 5 for charging, and discharges the storage battery 5 by a signal output when the generated power of the solar battery 1 is low. Numeral 7 is a reverse-current prevention diode.
The operation of the conventional low altitude satellite use power supply apparatus will be described below.
A current from a solar battery 1 is input into a power controller 3 through a reverse-current prevention diode 7 and a shunt apparatus 2. The power controller 3 supplies the current obtained from the solar battery 1 in shining hours to a load 6 and a charge controller 4a. The charge controller 4a generates a prescribed value of current IO shown in FIG. 7C by power from the power controller 3, supplies the current IO to a storage battery 5, and charges the storage battery 5. The voltage of the storage battery 5 increases as shown in FIG. 7B as the charging process advances. When the charge controller 4a detects that the voltage of the storage battery 5 reaches a predetermined temperature-compensated voltage value as shown in FIG. 7A (this is called V-T curve, in which 1xe2x88x92n lines are set by request), a charging mode of the charge controller 4 shifts from constant-current charging till then to constant-voltage charging. According to this, the charge current decreases taperingly as shown in FIG. 7C, and prevents over-charge to the storage battery 5.
On the other hand, in the time of shade, when the generated power of the solar battery 1 decreases, the charge controller 4a discharges the storage battery 5 by the output of the power controller 3, and supplies the power to the load 6.
The charge of the storage battery in the conventional low altitude satellite use power supply apparatus is performed as described above, however, the constant-voltage/constant-current charge as described above is conducted on the overall storage battery in which n battery cells are cascade-connected in series, therefore, there is a problem that a specific cell in the storage battery is overcharged due to the unbalance in charge characteristics of each cell constituting the storage battery. Specifically, in the Li-Ion (Lithium Ion) cell structured by Li (Lithium) electrode, energy density, charging voltage, discharging voltage, etc., are higher as compared to those of a Nixe2x80x94Cd cell, and the Li-Ion cell is expected for use in the storage battery, however, in the case of the Li-Ion cell, there is a problem that electrode deterioration is accelerated and the life is shortened when voltage of the cell exceeds a rated voltage and the cell is in the overcharged condition. For example, as the constant-voltage operating voltage in the V-T curve at the temperature of 0xc2x0 C., the sum of n cell voltage is detected as the storage battery voltage, and compared to the setting voltage, however, when m-th cell voltage is higher than that of the other cells due to the internal resistance of the cell, the voltage exceeds the upper limit of the cell voltage, sometimes resulting in deterioration of the cell.
The present invention is achieved to solve the above-identified problem and the object of the present invention is to obtain the battery accumulating apparatus by which an appropriate charge amount can be secured without overcharging each cell constituting the storage battery.
A battery accumulating apparatus of the first invention comprises a storage battery to which battery cells are cascade-connected, and a charge current generating means having a means which generates a plurality of different charge currents to charge the storage battery from the power supply output, and supplies the plurality of different charge currents to the storage battery.
In a battery accumulating apparatus of the second invention, in the first invention, the charge current generating means is provided with a means for generating a plurality of different charge currents, and for changing the charge current so as to be supplied at a low level after, initially, the charge current is supplied at a high level.
In a battery accumulating apparatus of the third invention, the charge current generating means is provided with a means for changing the charge current from a high level to a low level when any of voltage of battery cells reaches a prescribed value.
In a battery accumulating apparatus of the fourth invention, a shunt circuit is respectively connected to each battery cell, and when any of voltage battery cells reaches a prescribed value under the lowest level charge current supply condition to the storage battery, the charge current flowing to the battery cell is bypassed to the shunt circuit connected to the battery cell.
In a battery accumulating apparatus of the fifth invention, a switch is provided between the power supply and the storage battery, and normally is turned OFF, when in the ON status by the charge current generating means when any of voltage of battery cells reaches a prescribed value; and is returned to ON by discharge of the battery cells.
In a battery accumulating apparatus of the sixth invention, the charge current generating means is provided with a means which detects the voltage of the overall battery cell, and which shifts to constant-voltage charge control when the detected voltage reaches a prescribed value.
In a battery accumulating apparatus of the seventh invention, the charge current generating means is provided with a means which releases the constant-voltage charge control when the voltage of the plurality of battery cells becomes unbalanced, and charges the battery cells by the low level charge current until the voltage of the battery cells reaches a prescribed value.
In a battery accumulating apparatus of the eighth invention, a Li-Ion (lithium ion) battery cell structured by a Li (lithium) electrode is used as the battery cell.